Thanks for the input, @Marina! I'm looking for whatever words our users like the most in Russian. It doesn't necessarily have to be complicated or of a very advanced level. Simple things and simple words can be beautiful and meaningful as well :)

So whether you are a beginner or an advanced learner, let me know what your favourite words in the Russian language are :)

@uzgeorg both are correct, but have different meaning:
-мука́ is a flour;
-му́ка is a torment, torture, pain and suffering. Has quite a range of meanings from "муки творчества" - meaning a kind of artistic suffering that creative people have to go through to create something novel and beautiful, to "вечных мук" - kind of suffering one would experience in hell in order to repent.
So, which one is your word of choice?

Just a tiniest correction, @Michael-0. It definitely came from German, but it got "д" on the end along the way. So it's spelled "бутерброд". Also, there are lots of words borrowed from German that you may also like, for instance: шлагбаум, рюкзак, глюк (completely changed it's meaning) and so dear to a Russian soul word "блат".

I risk being expelled from this thread by the Russian linguist, but for the sake of frequency and because profanity is a powerful part of the Russian lexicon and is being equally studied by linguists, I must inform @Michael-0 that if he ever goes to Russia and hears блат pronounced as if with an umlaut, he should know it is profane and he should only use it against taxi drivers who are trying to charge him double.